The organic reactions that take place during the thermal coking of bitumen are extremely complex and deep-seated, but obviously hydrogen atoms originally attached to carbons that form coke will have moved to a new carbon site (net addition of hydrogen, resulting in upgraded bitumen). Accompanying this process, one expects some general hydrogen shuttling between non-coking molecules. This paper describes an approach to determing the extent of this latter process by the addition of a small amount of perdeuterated pyrene to the bitumen prior to the coking operation. The in situ pyrene functions as in indicator, allowing one to establish the extent and other mechanistic details of the "hydrogen donor" reactions that take place during coking. There is no indication that the pyrene substantially modifies the normal course of the reaction, hence the analogy to an indicator. Key words: bitumen coking, pyrene, hydrogen exchange, donor solvent, free radicals.
